1. Asteroid Belt Kuiper Belt Oort cloud
And Other minor Objects

3. Asteroid Belt Discovered in 1801.
Piazza found Ceres. Olbers found Pallas. Previously predicted by Franz Xaver VonZach.

4. Asteroid Belt
The region of space between Mars and Jupiter; about 2.8AU
Hundreds of thousands of asteroids known. Probably millions.
Three Largest
Vesta
Pallas
Hygiea

5. Asteroid Belt Asteroid belt: where most asteroids are.
At distance between 2 and 3.5 AU, between Mars and Jupiter
Three asteroids have diameter more than 300 km
About 200 asteroids are bigger than 100 km
Thousands of asteroids with diameters larger than 1 km
The vast majority are less than 1 km

6. Notable asteroids 4 Vesta 2 Pallas 10 Hygiea
Discovered in km X 460km
2 Pallas
Discovered in X 500km lighter materials than Vesta
10 Hygiea
Discovered in km X 431km

7. DAWN Spacecraft Launched in 2007
Mission to explore largest objects in the Asteroid Belt
Vesta arrived 2009
Discovered Vesta is a proto planet, not just any asteroid. It is differentiated and made up of different composition than most.
Ceres - by April of 2015

8. Vesta

9. Asteroid Belt 3 types of asteroid: Carbonaceous, Silicate, Metallic
Even the largest object in the belt, Ceres, is too dim to see without aid

10. Asteroid Belt
Remnants of a planet-formation process that failed

11. Asteroids outside the asteroid belt
Trojan asteroids
Two groups of asteroids orbit the Sun at distances similar to Jupiter, outside the asteroid belt. These are the Trojan asteroids.
Over 1,600 Trojan asteroids are catalogued.
Estimates of the their total number go up to tens of thousands.

12. Trojan asteroids trailing group
One group of Trojan asteroids is located at a stable point that trails Jupiter’s orbit by 60°.
Trojan asteroids leading group
Another group leads Jupiter by 60°.
There are slightly more leading that trailing Trojans.

13. The first Trojan asteroid was discovered in 1906.
The combined gravitational forces of Jupiter and the Sun in this 3-body rotating system produce these two regions where small bodies can have stable orbits.
French mathematician Louis Lagrange predicted the existence of these stable orbits, called Lagrange points, in 1772.
There are also three unstable points in such a system. The two stable Lagrange points are labelled L4 and L5. L5
The first Trojan asteroid was discovered in 1906. L4

14. Asteroid: outside the belt
NEO: near-Earth objects
Asteroids that cross Mars’s orbit due to high eccentricity, or whose orbits lie completely within that of Mars
More than 2500 near-Earth objects have been detected
If such an asteroid strikes the Earth, its effect depends on both the mass and the speed of the asteroid

16. Kuiper Belt Discovered in 1992
Named for Dutch Astronomer Gerard Kuiper, who had PREDICTED its existence in 1951.

17. Kuiper Belt Region beyond Neptune; 30 to over 50AU
At least small, icy, slow-moving, objects

18. Kuiper Belt
Very faint objects because small, far and reflect light from Sun
A million times fainter than faintest we can see with naked-eye

20. Oort Cloud Hypothetical spherical cloud. No direct observations.
Proposed by Ernst Opik (1932), Jan Henrik Oort (1950)

21. Oort Cloud 50 000AU; defines gravitational boundary of solar system
Source of long-period Comets

22. Oort Cloud Objects composed of ices (water, methane, and ammonia)
2 regions: outer sphere, inner disc

23. Oort Cloud Comets can not have formed on their current orbit
Must be held in an outer reservoir

24. Meteoroid, Meteor, Meteorite
Meteoroid: small chuck of rock in space
Like an asteroid but smaller
Asteroid generally larger than one hundred meters across
Meteor: the brief flash of light caused by a meteoroid when it enters the Earth’s atmosphere, and produces a fiery trail across the night sky
The glowing is the result of intense heat caused by atmospheric friction
Meteorite: If part of the object survives the fall, the fragment that reaches the Earth’s surface is called a meteorite

25. Asteroid: impact NEO: near-Earth objects
Mini-impact by meteorite : New York, Oct. 9, 1992
Tunguska Event: 1908
Seared and felled the trees in an area of 50 kilometer in diameter
By 80-m diameter asteroid

26. Asteroid: impact The Barringer Crater: 1.2-km wide. Arizona
An impact about 50,000 year ago
By a 50-m diameter iron-rich meteoroid

27. Asteroid: impact
An asteroid impact may cause the extinction of the dinosaurs and many other species 65 million year ago
An iridium-rich layer within limestone strata was discovered (1979)
Found at numerous site around the world
Geological dating reveals deposition 65 million years ago
By a 10-km diameter asteroid
The site is possibly the 180-km-diameter Chicxulub crater on the Yucatan Peninsula, Mexico (1992).

28. Meteorite
Meteorites are classified as stones, stony irons, or irons, depending on their composition
Stony meteorites account for about 95% of all meteoritic material that falls to the Earth
About 300 tons of extraterrestrial matter falls on the Earth each day, mostly in the form of dust.

29. Allende Meteorite (Mexico, Feb. 8 1969)
Meteorite: the Trace
Radioactive age-dating indicates that some meteorite is 4.56 billion years old, indicating the age of the solar system
Rare stony meteorites called carbonaceous chondrites may be relatively unmodified material from the solar nebula
These meteorites often contain organic material and may have played a role in the origin of life on Earth
Allende Meteorite (Mexico, Feb )

30. Comet
A comet is a chunk of mixture of ice and rock fragments that partially vaporizes as it passes near the Sun
Unlike asteroids, a comet generally moves in a highly elliptical orbit about the Sun

31. Comet: structure
Nucleus
Coma
Hydrogen envelope
Dust tail
Ion Tail

32. Comet: structure Nucleus
Solid part of comet from which coma and tails emanate
Mixture of ice and dust
Typically a few kilometer across
Coma
the fuzzy, luminous gas ball produced by the liberated gas as the comet near the Sun
Typically 1 million km in diameter
Tails
Caused by the luminous gas streaming outward
About 100 million km in length

33. Comet Halley. 1986 by Giotto spacecraft
Comet: structure
Nucleus
Comet Halley by Giotto spacecraft

34. Comet: structure

35. Comet: structure Dust tail
formed by the radiation pressure on the fine-grained dust particles in the coma
Radiation pressure: photons exerts a pressure on any object that absorbs or reflects it.
Dust particles slowly drift away forming a curved tail
Ion tail
Ionized atoms and molecules are swept directly away by the solar wind to form the relatively straight ion tail
The distinct blue color is caused by emission from carbon-bearing molecules such as CN and C2.

36. Comet: structure Hydrogen envelope
A huge sphere of tenuous hydrogen gas
Invisible in visible light, but visible in ultraviolet light
typically about 10 million km in diameter
Hydrogen comes from water molecules that break apart when they absorb ultraviolet photons from the Sun

37. Comet: Origin
Comets have highly elliptical orbits, indicating they come from the outer part of the solar system
Comets often have highly inclined orbits (not on the ecliptic plane), indicating a different origin from planets and asteroids

38. Comet: Origin From two large reservoirs: Kuiper Belt and Oort Cloud
lies in the plane of the ecliptic at distances between 30 (Neptune’s orbit) and 500 AU from the Sun
contain many tens of thousands of comet nuclei
Produce Jupiter-family comets, which orbits the Sun in fewer than 20 years and return at predictable interval
Oort cloud
A sphere extending from the Kuiper Belt to some 50,000 AU from the Sun
contains billions of comet nuclei
Intermediate period (20 to 200 years) and long-period comets (1 to 30 million years) are thought to originate in the Oort cloud

39. Comet: Meteor Shower
Meteoritic swarm: as a comet’s nucleus evaporates, residual dust and rock fragments form a loose collection of debris that continues to circle the Sun along the comet’s orbit
Meteor shower: it happens when the Earth’s orbit happens to pass through a meteoritic swarm

40. Comet: Meteor Shower

41. Comet: Meteor Shower

42. Sources
Universe: The Definitive Visual Guide